docs: def _validate_file_ownership(owner, group, file_name, optional=False):
      """
      Validate that a specified file is owned by `owner:group`.
  
      :param owner: Name of the owner
      :type owner: str
      :param group: Name of the group
      :type group: str
      :param file_name: Path to the file to verify
      :type file_name: str
      :param optional: Is this file optional,
                       ie: Should this test fail when it's missing
      :type optional: bool
      """
      try:
          ownership = _stat(file_name)
      except subprocess.CalledProcessError as e:
          print("Error reading file: {}".format(e))
          if not optional:
              assert False, "Specified file does not exist: {}".format(file_name)
      assert owner == ownership.owner, \
          "{} has an incorrect owner: {} should be {}".format(
              file_name, ownership.owner, owner)
      assert group == ownership.group, \
          "{} has an incorrect group: {} should be {}".format(
              file_name, ownership.group, group)
      print("Validate ownership of {}: PASS".format(file_name))